Or, let the beatings begin.
I started a new gig just about six months ago now and one of the goals I set for myself was to not fall into the trap of using bad visualizations. Have I been successful? Hard to tell yet, but it has taken an interesting turn – which could easily be defined as a failure . I’ve been proselytizing the use of Bullet Charts as a responsible replacement for gauges and dials. I’ve also been fostering the use of sparklines and clean charts in general. I’ve done really well with instituting sparklines and have raised the charting game of my co-workers.
However, Bullet charts have just not taken to the water.
That being said, I’ve campaigned heavily for their use over the past 6 months but ultimately, the report users just weren’t groking the chart and continually made mistakes in interpreting them. That’s not good. Misinterpretation can lead to the wrong insight or answer which leads to the wrong action.
So my boss says “Look, just give them a gauge – how about a speedometer chart?”
Then I explained all that was wrong with using speedometers in a business context and beyond that how hard they are to create and maintain.
That still left me with a problem though. the bullets weren’t hitting the target (har, har, har) and I needed a replacement. So, I grumbled a bit. Sighed and starting thinking about a gauge chart.
First, what are the typical problems with gauges as implemented in business dashboarding?
- They take up too much space (bad information-to-ink ratio)
- Low fidelity (data is not displayed with a high level of detail/resolution)
- A tendency to be visually imprecise – easy to tell if it’s bigger than a breadbox or smaller than a Volkswagen but assessing the actual value with any accuracy can be difficult
- May suffer from visual effects that create inaccuracies in interpretation (e.g. perspective, shadowing etc. create visual lies)
- All the other ones that I couldn’t think of – off the top of my head
OK, so to solve this correctly I needed to:
A. Maintain a (relatively) high information-to-ink ratio
B. Show the highest possible fidelity in the data
C. Show data precisely
D. Eliminate/Minimize distorting visual effects
Inspiraton: The picture in my head (hazy as it was) looked like some kind of decibel meter but this picture of an old pyrometer is also pretty close.
This old gauge is
- highly precise (to 1 degree Farenheit)
- relatively compact
- contains enough meta information to ward off imprecision in reading it
- can’t get away from red, yellow & green in a business dashboard
- related marker values – minimum, acceptable, target and goal
So what will we need to get the job done?
- Excel 2007
- Horizontal Bar Chart
- X/Y Scatter Chart
- XY Chart Labels Addon
There are many, many steps involved, which are covered in the xlsx download at the end of the post. The instructions assume a medium-to-expert level knowledge of charting in Excel. So, in order to keep this post relatively short, I won’t go through the steps here and leave that up to the download. Instead let’s take a look at the completed graph.
So here it is and it has only the vaguest relationship to the image above – right? About the only thing they have in common is the pointer.
BTW, I kinda like how Excel 2007 lets you use line ends (don’t remember that being in 2003/XP).
Alright, so what do we have going on here?
The chart is bounded by a box in a Dashboard. This box, by its title is “Page Views – Month to Date” so we know what we’re looking at. Immediately below the title we have the current count of page views (yeah, not a KPI [yet]) at 5 million in big, big text.
We can see that we’re in the red but closing on yellow. However, if we stopped here with no other cues it would look like page views are more than 50% along because our eye sees that the pointer has traversed most of the red.
But, we’re not done! There’s a custom X-Axis (courtesy of an XY Scatter) that the pointer points to and it shows that page views have traversed exactly 50% to the overall goal.
Of course, we could do the match in our heads (5 million is 50% of what?) but we’ve also got custom labels on the bar chart (our gauge background) so we know that our goal is 10 million page views, the minimum is 7 million and the target (minimum ‘acceptable’) is 9 million page views. Each of these markers in the gauge background are tied to a point on the x-axis so that we always know, with a high degree of accuracy, where we are, and where we want to get to. And notice how our non-KPI measurement of 5 million page views turns into a simple KPI as we measure it in terms of a goal – we’re 50% of the way there!
Lastly, this chart is no harder to maintain than a bullet chart is (actually, it’s just a bit easier/simpler).
So here are some questions for you:
Do you like the chart? Why/Why Not?
Is it a good chart? Why/Why Not?
What solutions have you used in the stead of something like a bullet chart because users just couldn’t get it?
Oh and here’s the file for you.
Update: After multiple requests, here’s some side-by-side screen shots of the line-gauge and a bullet chart based on a bullet chart I have blogged about previously.
As a bonus here is Peter Walker’s quick mockup
Now you have visual comparisons…